<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
<form>
<label>First name:</label> <input type="text" name="fname" /><br 
/>
<label>Last name:</label> <input type="text" name="lname" />
</form>
<script>
var $viewportMeta = $('meta[name="viewport"]');
$('input, select, textarea').bind('focus blur', 
function(event) {$viewportMeta.attr('content', 'width=device-width,initial-scale=1,maximum-scale=' + (event.type == 'blur' ? 10 : 1));
});
</script>
</body>
</html>